1. Field of the Invention
The present invention relates generally to the fields of molecular biology and cancer therapies.
2. Description of Related Art
The therapeutic use of proteins and peptides that act intracellularly holds much promise for the treatment of cancer and other diseases. However, the efficient introduction of polypeptides into cells has been difficult to achieve. Thus, new methods of introducing polypeptides into cells are needed.
Cancer is the result in the occurrence of multiple factors. Mutations may occur in proto-oncogenes that cause cellular proliferation to increase. Mutations also may occur in tumor suppressors whose normal function is to regulate cellular proliferation. Mutations in DNA repair enzymes impair the ability of the cell to repair damage before proliferating.
Tumor suppressor genes are normal genes whose absence (loss or inactivation) can lead to cancer. Tumor suppressor genes encode proteins that slow cell growth and division. Wild-type alleles of tumor suppressor genes express proteins that suppress abnormal cellular proliferation. When the gene coding for a tumor suppressor protein is mutated or deleted, the resulting mutant protein or the complete lack of tumor suppressor protein expression may fail to correctly regulate cellular proliferation, and abnormal cellular proliferation may take place, particularly if there is already existing damage to the cellular regulatory mechanism. A number of well-studied human tumors and tumor cell lines have been shown to have missing or nonfunctional tumor suppressor genes. Examples of tumor suppressor genes include, but are not limited to, the retinoblastoma susceptibility gene or RB gene, the p53 gene, the deleted in colon carcinoma (DDC) gene and the neurofibromatosis type 1 (NF-1) tumor suppressor gene (Weinberg, 1991). Loss of function or inactivation of tumor suppressor genes may play a central role in the initiation and/or progression of a significant number of human cancers.
Currently, there are few effective options for the treatment of many common cancer types. The course of treatment for a given individual depends on the diagnosis, the stage to which the disease has developed and factors such as age, sex and general health of the patient. The most conventional options of cancer treatment are surgery, radiation therapy and chemotherapy. These therapies each are accompanied with varying side effects and they have varying degrees of efficacy. Thus, there is a need to continue developing cancer therapies, including therapies based on tumor suppressor polypeptides.